Process of making sheet glass



Oct. 19 1926. 1,603,989

L. SHOWERS PROCESS OF MAKING SHEET GLASS Filed Jan. 18, 1926 I NVNTOR 0120. W

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pots, and then side which is to be exposed to View, and

I limited to the use of that Patented Oct. 19, 1926.

LEE sHownns, or QEARLEROI, PENNSYLVANIA, GLASS COMPANY, A CORPORATION PROCESS OF MAKING SHEET GLASS.

ASSIGNOR T PITTSBURGH IELA TE OF PENNSYLVANIA.

Application filed January 18, 1926. Serial No. SLMREISS The "invention relatesto an intermittent method of making glass-sheets... 'It has one of its largest fields of use in the makingof relatively thick colored glass, such as that known as carrara and used for architectural purposesin place of marble, but is not limited to such field, and may be employed to advantage in the manufacture of transparent'thick glass,.or of ordinary plate glass whichis ground and polishedin the usual way. 'Carrara glass, either black or white, is now made by casting in thick slabs from grinding and polishing the grinding (withoutpolishing) the other side which is not exposed to. view. .'The present process is designed to produt-e glass having a fire polished upper surface requiring no grinding and polishing and a lower surface which is substantially true and flat so that no grinding is required. In those cases in which a mechanically polished optically true upper surface is desired, the amount of grinding necessary is reduced to,';.'a minimum, so that the cost is materially lessened as compared with glass produced by the usual method. The form of apparatus preferably employed for producing the rolled sheet is that shown and described in my 00- 0 pending application. Serial Number 42,467,

filed July 9. 1925, but the method is not particular apparatus. Referring to the drawings:

Figure 1 is a vertical sectionithrough the rolling apparatus. And Fig. 2 is a vertical section through the complete apparatus in a very simple diagrammatic form.

Referring to the drawings,:.1 is a cast metal shell of large diameter which is in effect anannular casting table andvis supported upon a'pair of rolls 2 and 3 which extend through the rolls and are mounted in suitable bearings supported upon a framework 4 at each side of the shell The shell is heated before the first ca 'sting operation by means of the burners 5. The shell may be mounted so that its lower portion passes through the body of liquid 6.. which serves to cool the shell and keep it from becoming overheated. This cooling bathimay or may not be necessary. depending upon the speed of rotation of the shell and the frequency of the casting operations, the cooling effect of the atmosphere being relatively great upon a shell of large diameter. Any other glass which has been melted and form of cooling means may, of course, be employed. Mounted in opposition to the periphery of the annular shell 1 is a water cooled sizing roll 7, such roll being journaled in a tilting framework 8 pivoted to swing around the axis of the roll 3, so that the thickness of the sheet formed may be varied by swinging the roll up or down. This adjustment may be accomplished by means of threaded arms 9 pivotally connected at their lower ends to the framework Land having their upper ends extended through nuts 10 swiveled in an extension 11 secured to the tilting framework 8.

In advance of the shell 1 is a water cooled table 12 for supporting and chilling the lower surface of the glass sheet preliminary to its delivery upon the rolls 13, which rolls are artificially cooledeither by tion of air or water therethrough; These rolls extend in a continuous series through a long roller leer 14, which is several hundred feet in length and is provided with suitable temperature controlling means, so arranged that the temperature of the leer decreases progressively from its inlet to its outlet end, It is necessary to cool only the rolls in the first part of the leer, the rest of the rolls not requiring cooling and may be spaced at distances apart greater than that between the rolls at the entrance end of the leer and immediately following the table 12 where the glass is liable to sag due to its plastic condition.

A pocket 15 is provided between the shell 1 and the roll 7, the sides of this pocket being closed by means of end plates 17 which fit down between the rolls and prevent the body of glass from escaping laterally. The

pocket 15 is of relatively large capacity so that it may receive an entire pot of glass weighing a ten or more and capable of forming a sheet of glass anywhere from 40 to feet in length depending upon the thickness of the sheet. The sizing roll 7 and the 100 supporting rolls 2 and 3 are driven by suitable power means, not shown, preferably of the character illustrated and described in my pending application heretofore referred to. The rolls 13 which receive the glass af- 106 for it passes the table 12 are also driven at a rate of peripheral speed corresponding to that of the sizing roll 7and the shell 1.

In carrying out the operation, a pot of the circulafined in a 110 pot furnace is carried to a position over the pocket by means of, a crane and the contents emptied into the pocket. This is preferably done quickly, the capacity of the I pocket 15 being such as to receive the entire pot of glass before anysubstantial quantity is discharged between the shell and the sizing roll, although the rolling out of the sheet may be started, if desired, as soon as the 10 lower portion of the pocket is filled with glass. Better results are secured when the entire pot of glass is emptied into the pocket quickly than if a continued flow occurs from the'pot as the rolling progresses.

The rolling of the sheet 18 is preferably done at a relatively high rate of speed, ranging upward from 40 feet per minute, as compared with'a speed of rolling of 4 to 6 feet, such as is ordinarily employed in rolling 20- glass continuously from a tank. The high rate of rolling has been found to give glass with less mechanical ream, with less elongation of any bubbles in the glass and with a better surface than where such rolling is done more. slowly.

With. such high rolling speed, the chilling effect of the sizing roll 7 upon the surface of the glass is much reduced and .only a very thin chilled skin is formed. The marring effect of this roll upon the upper surface of the glass is, therefore, much reduced and in some cases entirely eliminated, particularly in the making of thick sheets of glass. Such sheets contain a large amount of residual heat, and after the sheet passes the sizing roll, and as it is carried along over the table 12 and the rolls 13, the top skin is softened up'by the volume of heat in the glass and flows somewhat, thus eliminating the marks of the roll and leaving the glass with a fire olish. This fire polish is comparable in egree with that secured in the ordinary plate glass polishing operation, but it is not opt cally plane and true due to the minute- 5 irregularities or waves which are always formed when the surface. of molten glass solidifies. If an optically true surface is desired, it is, therefore, necessary to grind and polish the upper surface of the glass, but this grinding and polishing is reduced to a minimum by the practice of the present process, and there is a wide field for the use of white and black glass in which an optically true surface is not required, the fire finish as secured by the present process being suflicient for the purpose. In such cases, the glass produced by the'present process requires no grinding or polishing either upon its upper or its lower surface. lVith colored glass for architectural work or for table tops, a lower polished surface is not necessary and the lower surface as produced by the present process is perfectly flat and true and relatively smooth. The present 9 process, therefore, produces a type of glass -ment must be continued for some time after the sheet enters the leer, otherwise, it will sag. If this rate of speed were continued throughout the entire annealing operation, a leer of enormous length would be required and the present procedure is designed to avoid this necessity in so far as is possible, an unusually long, leer being required in any case where sheets of unusual thickness are to be produced. It will be understood in this connection that the present process is designed to handle sheets both of unusual thi kness, such as those required for colored architectural glass and also for the production of plate glass of ordinary thickness. In either case the sheet is carried ahead at a high rate of speed until the glass has set sufiiciently, or the lower surface has set sufficiently, to prevent sagging. After the glass has so hardened and set the speed of rotation of the rolls in the leer in the section occupied by the glass at that time is reduced, and from such point on the sheet is given a speed of movement which is progressively less and less. Means are,therefore, provided for'driving the sets of rolls 13 in different sections of the leer at different rates of speed, so that the rate of movement of the sheet when it emerges from the leer is only a fraction of that at the. entrance end of the leer. By this procedure it is thus possible to roll the glass at a high rate of speed and stilLanneal it by a continuous process without making the leer of too great length.

Since the operation is an intermittent one,

it is possible to run the different sections of the leer at different speeds, such as would not be possible if a being formed.

What I claim is: 1. A process of making a glass sheet, which consists in rolling a body of molten glass laterally into a sheet at a relatively high rate of speed, carrying the sheet thus formed ahead on constantly shifting separated lines of transverse support, and then decreasing the speed of forward movement of the sheet and exposing it to a progressively decreasing temperature to anneal it. 2. A process of making a glass sheet, which consists in rolling a body of molten glass laterally into a sheet at a relatively hi h rate of speed, carrying'the sheet thus formed ahead on constantly shifting sepacontinuous sheet were lit) rated lines of transverse support, and then moves the marring efiect of the rolling 1 decreasing the s eed of forward movement means upon the u per surface ofthe sheet of the sheet and exposing it to a progresand gives afire p0 1sh or finish to such sursively decreasing temperature to anneal it, face.

the speed of rolling being such, and the In testimonywhereof, I have hereunto chilling efi'ect-of the upper rolling means subscribed my name this 12th day of Janu- 16 upon the sheet being reduced to a point ary, 1926. such, that the residual heat of the glass after passing the rolling means, substantially re- LEE SHOWERS. 

